agent-eval

Agent Eval Skill

A lightweight CLI tool for comparing coding agents head-to-head on reproducible tasks. Every "which coding agent is best?" comparison runs on vibes — this tool systematizes it.

When to Activate

• Comparing coding agents (Claude Code, Aider, Codex, etc.) on your own codebase
• Measuring agent performance before adopting a new tool or model
• Running regression checks when an agent updates its model or tooling
• Producing data-backed agent selection decisions for a team

Installation

Note: Install agent-eval from its repository after reviewing the source.

Core Concepts

YAML Task Definitions

Define tasks declaratively. Each task specifies what to do, which files to touch, and how to judge success:

name: add-retry-logic
description: Add exponential backoff retry to the HTTP client
repo: ./my-project
files:
  - src/http_client.py
prompt: |
  Add retry logic with exponential backoff to all HTTP requests.
  Max 3 retries. Initial delay 1s, max delay 30s.
judge:
  - type: pytest
    command: pytest tests/test_http_client.py -v
  - type: grep
    pattern: "exponential_backoff|retry"
    files: src/http_client.py
commit: "abc1234"  # pin to specific commit for reproducibility

Git Worktree Isolation

Each agent run gets its own git worktree — no Docker required. This provides reproducibility isolation so agents cannot interfere with each other or corrupt the base repo.

Metrics Collected

Metric	What It Measures
Pass rate	Did the agent produce code that passes the judge?
Cost	API spend per task (when available)
Time	Wall-clock seconds to completion
Consistency	Pass rate across repeated runs (e.g., 3/3 = 100%)

Workflow

1. Define Tasks

Create a tasks/ directory with YAML files, one per task:

mkdir tasks
# Write task definitions (see template above)

2. Run Agents

Execute agents against your tasks:

agent-eval run --task tasks/add-retry-logic.yaml --agent claude-code --agent aider --runs 3